Sequential high pressure-low pressure reforming



Nov. 19, 1963 v. o. BOWLES ETAL 3,111,430

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING Filed March 31, 1958 6Sheets-Sheet 1 IIO 2- 209 PSIG N 500 C so PSIG 94 95 53 I00 I02 04 I080.N. (R+3cc T.E.L.)

FIG. I

O U 5 .C o "6 a 2 Fl G. 2 (I) O U a. a: 5 E

INVENTORS VERNON O.BOWLES 00 I02 I04 I05 o WALTER F. READ Octane Numberof IO# RVP Product Nov. 19, 1963 v. o. BOWLES ETAL 3,111,480

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING Filed March 31, 1958 6Sheets-Sheet 2 0 o u 92 Hlgh Pressure 5 Effluent O.N.=9O z N H hPressurem '9 Fl G. 3 Effluent 0.N.=98

5 3 860 High Pressure 3 Effluent O.N.=94 g 040 O o 94 96 98 '00 I02 I04I06 I08 O.N.PRODUCT ago's mo e Octane Number (Rl3cc)of l0 RVP ProductINVENTORJ veauon 0.80WLES O.N.of FEED to Low Pressure Stage AGENT Nov.19, 1963 v. o. BOWLES EI'AL 3,111,430

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING Filed March 31, 1958 6Sheets-Sheet 3 as as V I IOI 0.N. IO RVP Product 2 (Low Pressure 1 IPrOdl-ICT) '04 II II I '05 a n Octane No. of High Pressure ProducHFeedto Low Pressure Stage) 0 a o N Io 203040506070 BOSOIOOI'OIZOBOHO DAYSonSTREAM INVENTURS vznuou o.a0wuzs warren P. am FIG.5

AGEN'IZ Nov. 19, 1963 v. o. BOWLES ETAL 3,111,430

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING 6 Sheets-Sheet 4 FiledMarch 31, 1958 5 Ma J M83 E Van m WM: NT n ww w @E b E N n. 7 GM N 0 203 2 1 2 u :50 A 0 mm a M m ONA d n w 0 H ud m mm w m M Q m m m m 3 M 5 Qu m 1 u m 5 m \J 5 8 nu Q wil m1 my r m 5 353 o.

Nov. 19, 1963 v. o. BOWLES ETAL 3,111,480

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFGRMING Filed March 31. 1958 6Sheets-Sheet 6 ms 31 m! we 3. 5 N! 3 5 o: .5 3 x. u \u Mm we m2 ZUIIOENEfimfim Mfimfi :3 33

3 \J on. w! my E 8. 5. n0. N2 .w. h m 1 m. 5. 3 m:

WALTER EREAD AGENT.

United States Patent 3,111,480 SEQUENTIAL HIGH PRESSURE-LOW PRESSUREREFORMING Vernon 0. Bowles, Rye, N.Y., and Walter F. Read, Westfield,N.J., assignors to Socony Mobil Oil Company, Inc., a corporation of NewYork Filed Mar. 31, 1958, Ser. No. 725,398 13 Claims. (Cl. 208-65) Thepresent invention relates to the production of gasolines havingsuper-octane ratings (research+3 cc. TEL) of 100 or more, particularly102 or higher and more particularly to the production of gasolineshaving the aforesaid super-octane ratings in a low pressure reformingoperation in which the octane rating research+3 cc. TEL) of the feed tothe low pressure reforming unit is within the range of about 81 to about98, preferably not greater than about 96, and the reaction temperatureand/or catalyst volume in the low pressure reforming unit is correlatedwith the octane rating (research-+3 cc. TEL) of the product and theoctane rating (research-H cc. TEL) of the feed to the aforesaid lowpressure reforming unit.

The present invention also relates to the production of gasolines havingsuper-octane ratings (research-H cc. TEL) of 100 or more particularly102 or higher, in which the naphtha is first reformed to a criticaloctane rating (research-{J cc. TEL) of 81 to 98, preferably not greaterthan 96, under high pressure, e.g., 500 p.s.i.g. or more and the productof the high pressure reforming operation is reformed at low pressure ofless than 500 p.s.i.g., e.g., p.s.i.g. to 450 p.s.i.g., to the requiredsuper-octane rating of 100 or more.

The present invention also relates to a combination of high pressurereforming (at 500 p.s.i.g. or more) with low pressure reforming (at lessthan 500 p.s.i.g.) in which the algebraic sum (EAT of the differencebetween the temperature of the vapors entering each reactor and thetemperature of the vapors leaving each reactor in the high pressure unitis equal to at least 2N R, where N is the volume percent of naphthenesin the naphtha charged to the high pressure unit and the algebraic sum(EAT of the difference between the temperature of the vapors enteringeach reactor and the vapors leaving each reactor in the low pressureunit is algebraically not more than N R, where N is the volume percentof naphthenes in the naphtha charged to the high pressure unit. In otherwords, where AT, is the difference between the temperature of the vaporsentering and the temperature of the vapors leaving reaction zone 1 ofthe high pressure unit, or the temperature drop across reaction zone 1,AT is the temperature drop across reaction zone 2 of the high pressureunit, and AT is the temperature drop across reaction zone 3 of the highpressure unit, then the sum of AT AT and AT is at least 2N.

Similarly, if AT is the temperature drop across reaction zone A of thelow pressure unit, and AT is the temperature drop across reaction zone Bof the low pressure unit, then the algebraic sum of AT and AT is notgreater than N R, where N is the volume percent of naphthenes in thenaphtha charged to the high pressure unit. The foregoing can beexpressed by two equations as follows:

The present invention relates specifically to the production ofgasolines having octane ratings (research+3 cc. TEL) of at least 100 byreforming a charge naphtha in the presence of hydrogen and aparticle-form platinumice type reforming catalyst at a reactor pressureof 500 p.s.i.g. or more and passing the high pressure effluent afterreduction of the pressure over a particle-form platinumtype catalyst atpressures less than 500 p.s.i.g., for example, 200 p.s.i.g.

The present invention provides a considerable saving in the total amountof reforming catalyst required in a combination unit comprising a highpressure reforming unit of one or more reactors and a low pressure unitof one or more reactors to produce a gasoline having a givensuper-octane rating from a given napththa when compared to the totalamount of reforming catalyst required to produce a gasoline of the samegiven superoctane rating from the same given naphtha wholly in a highpressure reforming unit or wholly in a low pressure reforming unit.Thus, the total reforming catalyst requirement of platinum-type catalystfor the present combination unit is about 25 to about 50 percent lessthan that required in a high pressure unit and about 35 to about 60percent less than that required in a low pressure unit.

The present invention also provides an advantage in increased on-streamtime between regencrations of at least 7 days when producing productshaving super-octane ratings (research-{4 cc. TEL) of about 104 orgreater and at least about 30 days when producing gasolines havingoctane ratings (research-k3 cc. TEL) of 104 or less, depending upon thespace velocity. As will be described later, less catalyst can be used,resulting in a higher space velocity and more rapid aging which is ofminor consequence when a regenerative system with a swing reactor isemployed.

The suggestion has been made in the past to reform naphtha sequentiallyat two reactor pressures. Thus, in 1943 Komarewsky and Riesz publishedan article in the Oil and Gas Journal in which they described a twostageprocess involving the use of relatively high and low reactor pressures.The following US. patents are directed to multi-stage reformingprocesses: 2,320,147; 2,338,573; 2,374,109; 2,409,695; 2,596,145;2,629,683; 2,654,694; 2,659,692; 2,664,386; 2,698,829; 2,710,826;2,710,827; 2,758,062; 2,773,013 and 2,773,014. The following Britishpatents also describe multi-stage reforming processes: 731,094; 742,966;745,520; 745,522; 773,- 476 and 775,961. However, the present inventionis not the discovery that the reforming reaction can be carried out athigh or low pressure or at high pressure and low pressure. The presentinvention results from the discovery that it is advantageous to controlthe octane rating of the feed to a low pressure reforming zone and thatthe reforming catalyst requirements are less for a combination unit thanfor a high pressure or a low pressure unit as described hereinbefore.

At the outset it is desirable to establish that the yield of 10 RVPgasoline at any octane rating is greater when the charge naphtha isreformed at relatively low reactor pressure, e.g., 200 p.s.i.g. thanwhen reformed at higher pressures, e.g., 500 p.s.i.g. Thus, aMid-Continent naphtha having a boiling range of F. to 380 F. wasreformed over a platinum-type catalyst comprising about 0.6 percent byweight platinum, about 0.6 percent by weight chlorine and the balancealumina at a reactor pressure of 500 psig. and a hydrogen-to-naphtharatio of 6 to l to produce 10 RVP gasolines of various octane ratings.The same charge stock was reformed over the same catalyst at a reactorpressure of 200 p.s.i.g. and a hydrogen-to-naphtha ratio of 6 to 1 toproduce 10 RVP gasolines having octane ratings of the same order ofmagnitude. The data thus obtained have been plotted to provide the graphFIGURE 1 in which curve A and curve B express the relationship betweenoctane number (research+3 cc. TEL) and the recovery of 10 RVP gasolineas percent by volume of the charge naphtha at a reactor pressure of 500p.s.i.g. and at a reactor pressure of 200 p.s.i.g. respectively.

It will be observed that at any octane number (research+3 cc. TEL) theyield of 10 RVP gasoline is greater when operating at 200 p.s.i.g. thanwhen operating at 500 p.s.i.g. (All octane ratings set forthhereinafter, unless noted otherwise, are research ratings with 3 cc. pergallon of tetraethy] lead added, i.e., research+3 cc. TEL.) Theincreased yield varies from 4 percent at 97 octane number to 8 percentat 105 octane number. Such an increased yield is of commerciallyimportant magnitude. However, reforming at relatively low reactorpressures, such as 200 p.s.i.g. while providing an increase of 10 RVPgasoline at octane ratings of the order of 90 to 108 also has thedisadvantages of (l) shorter catalyst life between regenerations, evenat lower space velocities, (2) more complex and more expensive processfacilities, (3) greater catalyst requirement, or (4) shorter on-streamtime per unit if non-regenerative.

The platinum-type catalyst described hereinbefore when used to reformnaphtha having an octane rating of 70 to 104 octane at 500 p.s.i.g. at agiven space velocity has an on-stream life between regenerations of atleast 180 days. On the other hand, the life of a platinum-type catalystwhen used to reform naphtha feed having an octane number of 70 togasoline having an octane number of 104 at pressures of the order of 200p.s.i.g. and at a given space velocity has an on-stream life betweenregenerations of only about 3 days.

It has now been discovered that, when producing 10 RVP gasolines havingoctane ratings within the range of about 100 to about 108, the on-streamtime between regenerations can be increased an industrially importantamount or the amount of catalyst required can be reduced considerablyfor substantially the same on-stream time by correlating the octanerating of the feed to a low pressure reforming unit with the octanerating of the 10 RVP gasoline to be produced in the low pressurereforming unit and with the reaction temperature and/or catalyst volumeof the low pressure reforming unit.

Thus, when producing 10 RVP gasoline having an octane rating of 106 at aspace velocity of 1.5 and a pressure of 200 p.s.i.g., an optimumon-stream time between regenerations of about 18 days can be obtained byensuring that the naphtha feed to a low pressure reforming unit has anoctane rating of about 95. Illustrative of the foregoing are thefollowing data:

Low Prcs- Low Pres- Days On- 10 RVP sure Reiormsure Reiormstream Be-Product ing Unit ing Unit, tween Re- Octane No. Charge Oc- 'lomp., F.generations tune N 0.

Compared with the on-stream period of 3 days when naphtha such asstraight run naphtha, having an octane number of about 70 is charged toa low pressure reforming unit, the on-stream period of 18 daysrepresents an increase of about 600 percent in the on-stream time. Inother words, when reforming naphtha to super-octane ratings of 100 ormore over a given amount of reforming catalyst a commercially importantincrease in the onstream time between regenerations can be obtained byregulating the octane number of the feed within critical limitsdependent upon the required octane rating of the product.

It is to be observed that when the naphtha is partially reformed underhigh pressure, i.e., 500 p.s.i.g., and then reformed to the requiredoctane rating under low pressure, i.e., 200 p.s.i.g., the yield ofgasoline from the combination unit is at least substantially the same asthat produced when the naphtha is reformed solely at a low pressure of200 p.s.i.g., for example, to super octane ratings of and more and inany event is substantially greater than when the naphtha is reformedwholly at a high pressure, e.g., 500 p.s.i.g. This is graphicallyillustrated by curve C in FIGURE 1.

Curve C in FIGURE 1 was plotted from the data obtained when aMid-Continent naphtha having a boiling range of F. to 380 F. wasreformed under the conditions set forth in Table I.

wt. percent Cl; balance alumina.

Operating Conditions High Prcs- Low Pressure Unit sure Unit Pressure,p.s.ig 500 200 llydrogen-to-naplitlia ratio 6 6 Space Velocity, vJhn/v.5 1. 5

l0 RVP GASOLINE Run No. Octane N umber Yield Volume Percent 05. 2 105. 390. 2 97. 8 99. 9 JG. 3 101. 0 94. 3 101. 2 .13. 2 102. 4 91. 2 I03. 080. 3 103. 8 88. 7 107. 0 81. 7

Table 11 Charge to reforming unit Mid-Continent naphtha. Boiling range180 to 380 F.

Sulfur Not 20 p.p.m. Nitrogen Not 1.0 p.p.m. Arsenic Not 0.005 p.p.m.Catalyst (both units) 0.6 wt. percent Pt; 0.6

wt. percent Cl; balance alumina.

Operating Conditions High Prcs- Low Pros sure Unit sure Unit Pressure,p.s.Lg 1. 500 200 1Iydrogen-to-naplitlia ratio [111 (111 Space Velocity,v .lhr/v 3 1. 5

Table II-Continued Yield 10# Octane No. RVP Gaso Octane No. Run Numberof Product line, Percent ol'lligh Pres- Volurnc of sure Efiiucnt ChargeAlthough the severity, i.e., octane number, of the conditions in thehigh pressure unit has no important effect upon the yield of 10 RVPproduct at any octane rating, it has been found that the octane numberof the efiiuent from the high presure unit does have an elfect upon thereactor temperature in the low pressure unit. The data establishing theforegoing are presented in Table III and plotted in FIGURE 3.

Table III Reactor Octane No. Octane No. 'Icrnnera- Run N0. High lrer-Product ture Low surc Elflucnt Pressure Unit 90. 7 05. 2 S02 90. 1 9?. 3834 91. 0 08. 9 848 90. 1 101. 0 809 90. (J 102. 1 858 00. 0 104 2 91593. 6 99. 9 842 94. 4 102. 4 80G 93. 6 103. 2 885 94. ii 104. 3 899 94.8 105. 2 921 94. l 107. 0 952 97. 8 90. 9 848 97. 0 101. 2 S63 97. 8100. 0 800 98. 104. 5 924 99. 0 105. 7 952 It has now been discoveredthat the octane number of the effluent of the high pressure stage is acritical factor in determining the reactor temperature required in thelow pressure stage to produce a 10 RVP product having a required octanenumber. This is important because the lower the reactor temperature toproduce a 10 RVP product having a required octane rating the longer theperiod between regenerations, i.e., the longer the on-stream period.

The on-stream period between regenerations is limited by the maximumtemperature to which the catalyst can be exposed during the reactionwithout permanent loss of activity and selectivity, hereinafterdesignated catalyst damaging temperature, and by the incrementalincrease in the reactor temperature required during the on-stream periodto produce a 10 RVP product having the required octane rating. Thus, forexample, some platinum-type catalysts are permanently deactivated whenexposed to temperatures of 1000 F. Therefore, in commercial operation toensure that there will be a minimum likelihood that permanentdeactivation will occur an upper temperature limit of 980 F. is placedupon the reactor inlet temperature. To cotninue to produce a 10 RVPproduct having a required octane rating employing the aforesaidplatinum-type catalyst it has been found that the average reactortemperature must be raised a fraction of a degree to as much as a fewdegrees Fahrenheit per day, depending upon the severity level. As aconsequence, the on-stream period between regenerations is dependentupon the initial reactor temperature required to produce a 10 RVPproduct having the required octane rating employing fresh or freshlyregenerated catalyst, hereinafter designated fresh catalyst. Thus,assume that to produce a 10 RVP product having an octane rating of 104the initial reactor temperature (employing fresh catalyst) is 900 F. andthat the limiting temperature is 980 F. Further, assume that theincremental temperature increase is 1.8F. per day. Then the on-streamperiod will be Thus, the lower the initial reactor temperature requiredto produce a 10 RVP product having the required octane rating whenemploying fresh catalyst, the other factors, permissible maximum reactortemperature and incremental rise in temperature being the same, thelonger the on-stream period between regenerations.

By an examination of the graph of FIGURE 4 those skilled in the art ofreforming will be assured that the maximum oil-stream time is correlatedwith the octane number of the feed and the octane number of the product.

The graph of FIGURE 4 of the drawings demonstrates the relation betweenthe octane number of the charge to the low pressure reforming unit andthe octane number of the 10 RVP product from the low pressure unit as afunction of the reactor temperature in the low pressure unit. That is tosay, the family of curves presented in FIGURE 4 demonstrates that as aresult of lower reaction temperatures, improved on-stream time betweenregenerations in a low pressure reforming unit employing a platinum-typcreforming catalyst is obtained by correlating the octane rating of thegasoline hydrocarbons of the charge to the low pressure reforming unitwith the octane rating of the 10 RVP product and the reactiontemperature with fresh catalyst. Thus, when a naphtha is subjected toconditions at 500 p.s.i.g. to produce a charge to a low pressurereforming unit having the octane ratings set forth in Table IV and thelow pressure unit containing a platinum-type reforming catalyst isoperated under conditions at 200 p.s.i.g. to produce 10 RVP prod uctshaving the required octane rating in excess of 100, the reactiontemperature in the low temperature reforming zone varies as the octanerating of the charge to the low pressure reforming unit varies.

The data presented in Table IV were read from the curves of FIGURE 3 andare plotted in FIGURE 4 as a family of curves for various average lowpressure reactor temperatures between 800 and 960 F. required to reformstocks, having various octane ratings, charged to the low pressurereforming unit to 10 RVP products having various octane ratings betweenand 108. The on-stream time in days between regenerations for operationsat each temperature are also presented in Table IV from the knowledgethat the average reactor temperature must be raised each day to maintainthe required product octane ratings. That is to say, the days on-stream,S at any reactor temperature, A, is determined from the relation betweenthe permissible maximum average reactor temperature, P, the reactortemperature, A, and the incremental rise in the reactor temperature indegrees Fahrenheit per day F required to maintain the required octanerating of the 10 RVP product as follows:

In Table IV the value of P is 980 F. and the values of F are asindicated.

= 44 days T able IV 10 RVP Product Low Pressure Low Pressure Octane N0.Stage Charge Reaction, S

Octane N0. Temp, F.

100 (F=0.0 F./D.) 90.2 860 133 91. 2 850 92. 3 840 156 93. 7 830 167 95.2 824 174 Q7, 1 830 167 97. 7 840 157 98.0 850 145 Table IVContinued 10RVP Product Low Pressure Low Pressure Octane No. Stage Charge Reaction,S

Octane No. Temp, F.

101(F=1.07 F./D.) 89.5 880 93 90. 6 $70 103 102 (F=1.28 FJD.) 89. 7 s9070 01. 2 880 T8 103 (F=1.52 F./D.)... 88.3 010 40 90. 1 900 53 104(F=1.80 F./D.) 85. 8 930 28 88. 4 920 33 105 (F=2.15 F./D.). 86.1 940 1989. 0 930 23 106 (F=".58 FJD.) 86.6 950 2 90. 0 940 15. 5

107 (F=3.05 RID.) 86. 8 060 7 9'2. 0 050 From the foregoing data itbecomes manifest that the maximum on-stream time between regencrationsis obtained when operating a low pressure, i.e., 100-4S0 p.s.i.g.,preferably 200 p.s.i.g., reactor at the low pressure reactortemperatures correlated with the octane rating of the charge and theoctane rating of the 10 RVP product.

The values for S in Table IV have been plotted in FIGURE 5 against theoctane rating of the gasoline hydrocarbons of the charge for each 10 RVPproduct having an octane rating between 101 and 107. From the curves inFIGURE 5 broad and preferred ranges of the octane ratings of thegasoline hydrocarbons in the charge required to produce a RVP producthaving an octane rating within the range of about 101 to about 107 canbe read off. These ranges are tabulated in Table V.

Table V Octane N0. 01 Reaction Temp, Gasoline Hydro- F. with Freshcarbons of Charge Days Orr-Stream Catalyst at Low Product to the LowPres- Pressure sure Unit Broad Preferred Broad Preferred Broad PreferredAccordingly, the present invention provides a method for reformingnaphtha to produce 10 RVP products having octane ratings of at least 100which comprises reforming a charge stock having an octane number of atleast about 87 and not more than about 98 and preferably at least about91 and not greater than about 97 in the presence of hydrogen at ahydrogen-to-cliargestock mol ratio of about 2 to 10, preferably 3-6, anda platinum-type catalyst at initial reactor temperatures within therange of about 810 and on-stream final reactor temperature of themaximum temperature to which said platinum-type catalyst can besubjected without permanent loss of activity and selectivity and at aspace velocity (v./hr./v.) of about 0.5 to about 5.0.

It will be observed that the present invention provides a method forreforming naphthas to produce 10 RVP products having an octane rating of104 with an onstream time between regenerations of about 30 to about 40days. The importance of this advance in the art will become manifestwhen it is understood that commercially a 10 RVP product having anoctane rating (research clear) of 100 equivalent to 104 (research-H cc.TEL) is being produced employing five reactors and a swing reactor andregenerating two of the reactors in each 24 hours. Thus, the averageon-stream time is 3 days. In addition, when the on-stream time issubstantially the same, i.e., two days but the octane rating of thegasoline hydrocarbons of the feed to the low pressure reforming unit iscorrelated with reaction temperature in the low pressure reforming unitonly about 35-50 percent as much catalyst is required as is required inthe prior art low pressure reforming processes. (See Table VIII.)

It is also to be recognized that in the present sequential highpressure-low pressure combination the catalyst bed exposed to reformingconditions of high severity is doubly protected against contaminationwith arsenic and/ or lead and/or other metals in the feed naphtha. Thatis to say, the total unit, i.e., pretreater, high pressure reformingunit, and low pressure reforming unit, is designed to removecontaminants including arsenic, lead, etc. in the pretreater. However,in the event of failure, human or mechanical, of the prctreatcr, thecatalyst employed in the low pressure unit where the catalyst is exposedto conditions of higher severity is still protected by catalyst in thehigh pressure unit.

The combination of sequential high pressure-low pressure reformingprovides another advantage which is not obvious. Thus, while in priorart low pressure reforming units less hydrogen and light hydrocarbonswere circulated, on the other hand, it was necessary to have a largenumber of reactors each containing substantially the same amount ofcatalyst to provide capacity necessary to take care of the largeendothermicity. In contrast in the present sequential high pressure-lowpressure combination it is not necessary to provide a low pressure unitof sufficient size to meet the requirements of the large endothermicityof the reaction. That is to say, in the present sequential highpressure-low pressure reforming process the algebraic sum of thedifferences between the vapor inlet temperatures and the vapor outlettemperatures of the reactors of the high pressure unit is at least about2N F. (as defined hereinbefore) whereas in the low pressure unit of thecombination unit the difference in temperature between the inlettemperatures and the vapor outlet temperatures of the reactors is notgreater than about N F. In other words, sequential high pressure-lowpressure reforming is a reforming process wherein in an adiabatic systemthe heat loss due to the endothermic heat of reaction is at least about2N F. in the high pressure unit and not greater than about N F. in thelow pressure unit.

The presently preferred method of applying the principles of the presentinvention to the production of 10 RVP product having octane ratings ofthe order of 100 and greater is that illustrated in FIGURE 6.

While the pretreatment of the naphtha to reduce the sulfur content toless than 20 p.p.m., the nitrogen content to less than 1 p.p.m., and thearsenic content to less than 0.005 p.p.m., preferably 0.002 ppm. is nota part of the present invention, the pretreatment of the naphtha, i.e.,hydrotlecontamination of the naphtha, as well as the presently preferredmethod of producing 10 RVP gasoline having octane ratings in excess of100 is illustrated in FIGURE 6. The flow sheet presented as FIGURE 6illustrates decontamination of a charge naphtha and reforming of thehydrodecontaminated naphtha in the presence of a particle-formplatinum-type reforming catalyst in the presence of hydrogen at highreactor pressures of at least 500 p.s.i.g. followed by reforming at lowpressure, i.e., less than 500 p.s.i.g.

Thus, charge naphtha containing not more than about 12 p.p.m. ofnitrogen flows from a source not shown through pipe 1 to the suctionside of pump 2. Pump 2 discharges the charge naphtha into pipe 3 at apressure to cause the naphtha to flow from pump 2 into absorber 6. Thecharge naphtha flows through pipe 3 to pipes 4 and 7 and thence toabsorber 6. Gas containing hydrogen derivatives of the contaminantspresent in the charge naphtha flows from stripper 42 and separator 34through conduits 43 and 35 respectively to conduits 10 and 12. Theamount of gas flowing through conduit 10 is controlled by valve 11. Theamount of charge naphtha flowing through pipe 4 is controlled by valve5. These respective amounts of gas and charge naphtha are balanced toprovide for the removal of light hydrocarbons from the gas and theremoval of water and oxygen from the charge naphtha. This avoidsrecycling of the contaminant derivatives through the pretreatingsection.

The charge naphtha and absorbed hydrocarbons flow from absorber 6through pipe 13 to the suction side of pump 14. Pump 14 discharges thecharge naphtha into pipe 15 at a pressure greater than the pressure inreactor 26. The charge naphtha flows through pipe 15 to heat exchanger16. In heat exchanger 16 the charge naphtha is in indirect heat exchangerelation with the effluent from hydrodecontaminator 26 flowing theretothrough conduit 30.

From heat exchanger 16 the charge naphtha flows through pipe 17 to heatexchanger 18 where the charge naphtha is in indirect heat exchangerelation with the effluent from hydrodecontaminator 26 flowing throughconduit 27. From heat exchanger 18 the charge naphtha flows through pipe19 to coil 29 in furnace 21.

In coil 20 the charge naphtha is heated to a temperature within therange of about 600 to 750", preferably 675 to 725 F. The heated chargenaphtha flows from coil 20 through pipe 22 to conduit 23 where it ismixed with hydrogen-containing gas flowing from compressor 69 and/orstripper 42 through conduits 100 and 24 or 43. 44 and 24 respectively.

The mixture of charge naphtha and hydrogen-containing gas flows throughconduit 23 into hydrodecontamina tor 26. In hydrodecontaminator 26 thecharge naphtha contacts catalyst having hydrogenating and desulfurizingand denitrogenizing capabilities. Typical of such catalysts are thosecomprising a mixture of oxides of cobalt and molybdenum well-known tothe art. For example, a decontaminating catalyst comprising about 3percent by weight of cobalt oxide, about 15 percent by Weight ofmolybdenum oxide and the balance substantially alumina can be used.Reaction temperatures within the range of about 600 to 800 F. areemployed with space velocities of about 1 to 7 v./hr./v. inhydrodecontaminator 26.

The effluent from :hydrodecontaminator 26 flows through conduit 27 toheat exchanger 18 where the efliuent is in indirect heat exchange withthe charge naphtha as described hereinbefore. From heat exchanger 18 theeffluent flows through conduit 28 to heat exchanger 29 where theeffluent is in indirect heat exchange relation with thehydrodecontaminator condensate flowing from pump 37 and heat exchanger39 through pipe 40. From heat exchanger 29 the effluent flows throughconduit 30 to heat exchanger 16 where it is in indirect heat exchangerelationship with absorber bottoms. From heat exchanger 16 the effluentflows through conduit 31 to cooler 32 where the efiiuent is cooled to atemperature such that C and heavier hydrocarbons condense at thepressure existing in liquid-gas separator 34. The pressure in sep- 10arator 34 is usually within the range of about 400 to about 450 psig.

In liquid-gas separator 34 the hydrogen and some of the derivatives ofsulfur, nitrogen, arsenic and the like together with some of the C andlighter hydrocarbons separate and flow therefrom (as described brieflyhereinbefore) through conduit 35 to conduits 10 and 12 and thencethrough absorber 6 to be vented through conduit 121 to the refinery fuelsystem.

The condensed and separated C and heavier hydrocarbons together withsuch amounts of the hydrogen derivatives of the contaminants as aresoluble in the hydrodecontaminator condensate at the temperature andpressure existing in separator 34 flow from separator 34 through pipe 36to the suction side of pump 37. Pump 37 pumps the hydrodecontaminatorcondensate through pipe 38 to heat exchanger 39 where thehydrodecontaminator condensate is in indirect heat exchange relationshipwith the bottoms of stripper 42 flowing therefrom through pipe 46. Fromheat exchanger 39 the hydrodecontaminator condensate flows through pipe40 to heat exchanger 29 where the hydrodecontaminator condensate is inindirect heat exchange relation with the total efflu ent flowing fromhydrodecontaminator 26 as described hereinbefore. In heat exchanger 29the hydrodecontaminator condensate is heated to a temperature at whichthe dissolved hydrogen derivatives of the contaminants can be strippedfrom the hydrodecontaminator condensate with a stripping gas as hydrogencontaining recycle gas. The hydrodecontaminator condensate usually isheated to about 300 to 400 F. in heat exchanger 29. From heat exchanger29 the hydrodecontaminator condensate flows through pipe 41 to stripper42. Hydrogen-containing recycle gas flowing from turbo-compressor 69through conduits 100 and 95 strips the dissolved gases from thehydrodecontaminator condensate. The stripping gas and stripped volatilesflow from stripper 42 through conduit 43 to conduit 12 and absorber 6.When required the hydrogen stripping gas can be diverted wholly or inpart through conduit 44 under control of valve 45 to supply all or partof the hydrogen required in hydrodecontaminator 26.

The bottoms of stripper 42 comprising C and heavier hydrocarbonscontaining less than 20 ppm. of sulfur, less than 1 ppm. of nitrogen,and less than 5 p.p.b., preferably 2 p.p.b., i.e., less than 0.005,preferably less than 0.002 ppm. of arsenic flows from stripper 42through pipe 46 to heater exchanger 39 where the bottoms, hereinafterdesignated high pressure feed, is in indirect heat exchange relationwith the hydrodecontaminator condensate as described hereinbefore. Fromheat exchanger 39 the high pressure feed flows through pipe 47 to thesuction side of pump 48. Pump 48 discharges the high pressure feed intopipe 49 at a pressure greater than the pressure in high pressure reactor58.

Low pressure hydrogen-containing recycle gas (obtained as hereinafterdescribed) flows from steam driven compressor 98 through conduit 99 toconduit 50 at a pressure in excess of that of reactor 58. In conduit 50the high pressure feed flowing thereto through pipe 49 and thehydrogen-containing recycle gas flowing thereto through conduit 99 aremixed in the ratio of about 2 to 10 mols of hydrogen per mol of naphthain the high pressure feed to form a high pressure charge mixture.

The high pressure charge mixture flows through conduit 50 to heatexchanger 51 where the high pressure charge mixture is in indirect heatexchange relation with the low pressure effluent flowing from the lowpressure reactor on-stream through conduits and 86. The high pressurecharge mixture flows from heat exchanger 51 through conduit 52 to heatexchanger 53 where the high pressure charge mixture is in indirect heatexchange relation with the total low pressure efliuent flowing throughconduit 89.

From heat exchanger 53 the high pressure charge mixture flows throughconduit 54 to coil 55 in heater 56. In coil 55 the high pressure chargemixture is heated to a reforming reaction temperature below the maximumpermissible catalyst temperature dependent upon the activity of thecatalyst and the octane rating required for the feed to the low pressureunit to provide improved onstream time in the low pressure unit at theoctane rating required for the 10 RVP product of the low pressure unit.

The following low pressure reaction temperatures have been found to givesatisfactory results leading to improved on-strearn periods or toreduced catalyst requirements as described hereinbefore.

1 For incremental increase in reactor temperature to maintain requiredoctane rating refer to Table IV.

However, the high pressure unit is oprated under conditions oftemperature and space velocity to provide high pressure eflluent, i.e.,low pressure feed, the gasoline hydrocarbons of which have the octaneratings required to give improved on-strcarn time for the low pressurereactor or reduced total catalyst requirements. Illustrative ranges ofthe octane ratings of the gasoline hydrocarbons in the feed to the lowpressure reforming unit are given in Table VII.

Table VII Low Low Pressure Pressure 10 RVP Pl'OllllCt Octane. Relorin-Reform 5180" I S ing Unit ing Unit, A11, 1*.

Charge ]e|np., Octane F.

107 (Aging rate 3.05 F.fD.) 86. 952 28 .1 J0. 7 1 D48 32 11 93. 5 952 289 I06 (Aging rate 258" F./l).,l S7. 5 940 40 .13. l 1 H34 46 18 913.694.0 40 15 105 (Aging rate 215 F.."D.) S6. 8 s 50 23 U4. 1 tll l 66 31U8. 2 930 50 23 101 (Aging ruin LEO F.ll).) 86. (l 920 (ill 33 94, 5 1tlll Ni 48 100. 0 J30 5U 28 103 (Aging rate 162 11/17.)" 87.1 910 70 46M. S 1 873 10? TL) 99. l 910 TU 46 102 (Aging ratc 128 Hill) 85. 3 91070 55 15. 0 1 85-1 12G 98 E18. 0 S90 90 70 101 (Aging rate 107 F./D.)83.8 910 70 05 95. 1 l 833 147 137 97, 8 860 120 112 100 (Aging rate 0.9I., D.) 82. 4 H10 70 78 95. 2 1 M5 165 173 98. U 850 130 145 1 Presentlypreferred vapor inlet. temperature to low pressure reforming unitemploying hereinbelore described platinum catalyst containing 0,6 weightpercent platinum.

The heated high pressure charge mixture flows from coil 55 throughconduit 57 to reactor 58 where the high pressure charge mixture iscontacted with platinum-type reforming catalyst comprising, for example,0.6 percent by weight platinum, 0.6 percent by weight chlorine, and thebalance, to 100 percent by weight, alumina at an overall space velocitywithin the range 0.510 v./hr./v. The high pressure charge mixture flowsdownwardly through reactor 58. The eflluent of reactor 58 flows throughconduit 59 to coil 60 in heater 56 where it is reheated to a reactiontemperature the same as, lower or higher than, the temperature ofreactor 58.

From coil 60 the reheated first reactor effiuent flows through conduit61 to reactor 62 where the reheated first reactor efiiuent is contactedwith a platinum-type catalyst preferably the same as that in reactor 58for economic reasons. The efliuent of reactor 62 flows through conduit63 to coil 64 in heater 56 Where the second reactor efiluent is reheatedto reaction temperature the same as, or lower or higher than thetemperatures in reactors 58 and 62.

From coil 64 the reheated second reactor effluent flows through conduit65 to reactor 66. In reactor 66 the reheated second reactor efiluent iscontacted with a platinum-type catalyst, preferably the same type ofcatalyst as used in reactor 58 and 62 for economic reasons. From reactor66 the third reactor ei'liuent flows through conduit 67 to the turbineside 68 of turbo-compressor 69. In the turbine 68 the pressure of thethird reactor efiluent is reduced to that of the low pressure reactorplus the pressure drop from turbine 68 t0 the low pressure reactors. Theturbine 68 drives the compressor 69 which compresses the low pressurerecycle gas (obtained as hereinafter described) to the pressureattainable from the power in turbine 68.

From turbine 68 the third reactor eflluent comprising naphtha having anoctane rating dependent upon the octane rating required for the i0 RVPproduct of the low pressure unit to provide improved on-stream time forthe low pressure unit for 10 RVP products having octane ratings of about100 to about 107 and hydrogen, hereinafter designated low pressurecharge mixture, flows through conduit 70 to coil 71 in heater 72. Incoil 71 the low pressure charge mixture is heated to a reactiontemperature required to produce a 10 RVP product having the requiredoctane cating. Thus, the reaction temperature to which the low pressurecharge mixture is heated in coil 71 is Within the range about 830 to 980F.

From coil 71 the low pressure charge mixture flows through conduit 73 tomanifold 74 and thence through manifold branch 75 or 76 to reactor 79 or80 depending upon which reactor is on-stream. For purposes ofillustration, reactor 79 is on-stream and reactor 80 is in theregeneration portion of the cycle. Accordingly, valves 73 and 84 areclosed in conduits 76 and 82 respectively and valves 77 and 83 are openin conduits 75 and 81 respectively. With these valve settings the lowpressure charge mixture flows from coil 71 through conduit 73. manifold74, and manifold branch 75 to reactor 79. The effluent from reactor 79flows through manifold branch 81 to manifold 85 and thence throughconduit 86 to heat exchanger 51. In heat exchanger 51 the low pressureeffluent is in indirect heat exchange relation with the low pressurecharge mixture as described hereinbcfore.

From heat exchanger 51 the low pressure efilucnt flows through conduit87 to heat exchanger 88. A part of the low pressure efiluent by-passesheat exchanger 88, flowing through conduit 90 under control of valve 91to conduit 89. The balance or all of the low pressure effluent fiOWsthrough heat exchanger 88 where the low pressure effluent is in indirectheat exchange relation with a portion of the bottoms of stabilizer 104.The amount of low pressure efiluent flowing through heat exchanger 88 isproportioned to the fractionation desired in stabilizer 104 usually tomaintain a temperature in stabilizer 104 at which n-C and lighterhydrocarbons are volatile. From heat exchanger 88 the low pressureeliluent flows through conduit 89 to heat exchanger 53 where the lowpressure efilucnt is in indirect heat exchange relation with the highpressure charge mixture as described hercinbcforc. From heat exchanger53 the low pressure effluent flows through 13 conduit 92 to cooler 93where the temperature of the low pressure effluent is reduced to that atwhich C and heavier hydrocarbons condense. From cooler 93 the condensedand uncondensed constituents of the low pressure efiluent flow throughconduit 94 to liquid-gas separator 95.

In liquid gas separator 95 the uncondensed constituents of the lowpressure efiluent, i.e., propane and lower boiling hydrocarbons, andhydrogen separate from the higher boiling hydrocarbons. The uncondensedconstituents of the low pressure effluent, hereinafter designatedhydrogen-containing low pressure recycle gas, flow from liquidgasseparator through conduit 96 to turbo-compressor 69.

In turbo-compressor 69 the hydrogen-containing low pressure recycle gasis recompressed to as high a pres sure as practical employing the highpressure reactor eflluent as the driving medium for turbo-compressor 69as described hereinbefore. Turbocornpressor 69 discharges the compressedhydrogen-containing low pressure recycle gas into conduit 97. A portionof the compressed hydrogen-containing low pressure recycle gas, which isabout equal to the gas produced in the reactors of the combination unitis diverted through conduit 100 under control of valve 122 to stripper42 and to hydrodecontaminator 26 as required, as described hereinbefore.The balance and preponderant portion of the compressedhydrogen-containing low pressure recycle gas flows through conduit 97 tosteam-driven compressor 98. In compressor 98 the compressedhydrogen-containing low pressure recycle gas is further compressed to apressure greater than the pressure in reactor 58 to compensate for thepressure drop between compressor 98 and reactor 58. The pressurizedhydrogen-containing low pressure recycle gas, hereinafter designatedhigh pressure recycle gas, flows from compressor 98 through conduit 99to conduit 50 where the high pressure recycle gas is mixed with the highpressure charge naphtha as previously described hereinbefore. (Thoseskilled in the art will recognize that the use of turbo-compressor 69 isnot essential to the present invention and that the pressure of the highpressure recycle gas can be reduced to that of the low pressure systemby means other than turbo-compressor 69, for example, a reducing valve.)However, it is presently preferred to use the high pressure recycle gasas the driving fluid in turbocompressor 69 to raise the pressure of thelow-pressure recycle gas to a pressure somewhat less than that requiredin the high pressure unit and to complete the compression of the lowpressure recycle gas to the pressure required in the high pressure unitwith steam-driven compressor 98.

Returning to liquid-gas separator 95; the condensed constituents of thelow pressure efiiuent, i.e., isob-utane and higher boiling hydrocarbons,hereinafter designated condensate, separate as a liquid in liquid-gasseparator 95. The condensate flows from liquid-gas separator 95 throughpipe 101 to heat exchanger 102 where the condensate is in indirect heatexchange relation with the bottoms of stabilizer 104. From heatexchanger 102 the heated condensate flows through pipe 103 to stabilizer194. In stabilizer 104 C and lighter hydrocarbons are taken overheadthrough pipe 105 to cooler 106 and thence through pipe 107 toaccumulator 108. The temperature in accumulator 108 is maintained tocondense the heavier hydrocarbons. The condensed hydrocarbons,hereinafter designated accumulator condensate, flow through pipe 111 tothe suction side of pump 112. Pump 112 discharges into pipe 113 throughwhich the accumulator condensate flows to stabilizer 104 for use asreflux therein. A portion of the accumulator condensate is divertedthrough pipe 114 under control of valve 123 to suitable means forrecovering isobutane for feed to an alkylation unit and for recoveringnormal butane for admixture with the higher boiling reformate to providethe required Reid vapor pressure of the super-octane product.

A portion of the bottoms of stabilizer 104 flows through pipe 119 toheat exchanger 88 where the stabilizer bottoms is in indirect heatexchange relation with the low pressure effluent. The stabilizer bottomsis heated in heat exchanger 88 to a temperature at which C hydrocarbonsare volatilized. The heated stabilizer bottoms flows from heat exchanger88 through pipe back to stabilizer 104. Any other form of re-boiler canbe substituted for that illustrated. Furthermore, any other means formaintaining a temperature in stabilizer 104 at which C hydrocarbons arevolatile can be substituted for the means illustrated.

The balance, and major portion of the stabilizer bottoms, flows fromstabilizer 104 through pipe 115 to heat exchanger 102 where thestabilizer bottoms is in indirect heat exchange relation with the lowpressure condensate flowing from separator 95 through pipe 101 asdescribed hereinbefore. From heat exchanger 102 the stabilizer bottoms,hereinafter designated reformate, flows through pipe 116 to cooler 117.In cooler 117 the reformate is cooled to a temperature at which thelowest boiling constituent is liquid at atmospheric pressure. Fromcooler 117 the reformate flows through pipe 118 to storage.

Alternatively, as shown in FIGURE 7, the low pressure reforming unit canconsist of two low pressure, e.g., 15 to 450 p.s.i.g., reactors plus alow pressure swing reactor, with means for reheating the effluent of thefirst reactor of the pair on-stream prior to introducing the effluentinto the second reactor of the pair on-stream. The low pressure chargemixture is heated to the desired reaction temperature (as describedhereinafter) in coil 124 of heater 125. The heated low pressure chargemixture fiows from coil 124 through conduit 126 to manifold 127 andthence through manifold branches 128 or 129 or 130 dependent upon whichreactor of the pair on-stream is the first reactor to which the lowpressure charge mixture flows. For the purpose of illustration, it willbe assumed that reactor 133 (the swing reactor) is in the regenerationportion of the recycle and that reactor 131 is the first of the pair ofreactors which is on-stream. Accordingly, with valves 134, 138, 147 and161 open and with valves 135, 136, 137, 139, 146, 148, 162, and 163closed, the low pressure charge mixture flows from manifold 127 throughmanifold branch 128 to reactor 131. The charge mixture flows downwardlythrough the bed of catalyst in reactor 131 to conduit (valve 134 open;valve 137 closed) to effluent reheat manifold 153. The efiluent fromreactor 131, hereinafter designated first efiluent, flows throughconduit 155 to coil 156 in heater 125.

In coil 156 the first effluent is reheated to a reaction temperature thesame as, higher or lower than, the temperature to which the low pressurecharge mixture was heated in coil 124. From coil 156 the re-heated firsteffluent flows through conduit 157 to manifold 152 having branches 149,and 151. The re-heated first effluent flows through manifold branch 150(valves 146, 148, and 162 closed; valve 147 open) to reactor 132. Thereheated first efiluent flows downwardly through the catalyst bed inreactor 132 to conduit 141. From conduit 141 the efiluent from reactor132 hereinafter designated final low pressure efiiuent, flows throughconduit 144 (valve 135 closed; valve 138 open) to low pressure finaleflluent manifold 154. From low pressure final effluent manifold 154 thelow pressure final efituent flows through conduit 86 to heat exchangers51, 88 and S3 and cooler 93 to separator 95 for the purposes describedin the discussion hereinbefore of the flow of the effluent from thealternate low pressure unit.

tI will be observed that the piping required for regeneration of thedeactivated catalyst in the reactors of the high and low pressure unitshas not been illustrated in FIG- URES 6 and 7. Since the methods ofregenerating fixed beds of catalyst are well known to those skilled inthe art, it has been considered unnecessary to illustrate the pipingrequired for regeneration of the catalyst in the low or high pressurereactors.

While the flow sheet of FIGURE 6 does not provide for the introductionof extraneous gasoline hydrocarbons having octane ratings of about 81 to98 it is to be understood that the low pressure reforming unit can bedesigned for a capacity in excess of capacity required for treating theeflluent of the high pressure reforming unit and extraneous gasolinehydrocarbons treated in conjunction with the effluent of the highpressure reforming unit. Thus, a straight run naphtha or a fraction ofcracked gasoline, for example, catalytically cracked gasoline, can bemixed with the effluent from the high pressure reforming unit inproportions to provide a feed to the low pressure reforming unit havingan octane rating within the range 81 to 98 dependent upon the requiredoctane rating of the 10 RVP gasoline (containing process butanes)produced in the low pressure unit and the mixture reformed in the lowpressure reforming unit to the required octane rating.

Savings in catalyst inventory of considerable magnitude are provided bythe hereinbefore described combination of sequential high pressurereforming-low pressure reforming when compared with catalyst inventoriesrequired for producing a product having the same octane rating either byreforming entirely at high pressure or by reforming entirely at lowpressure. The data presented in Table VIII show that the differences incost of catalyst inventory to produce the same amount of product havingan octane number of about 106 can amount to as much as $719,000 to$1,580,000 in a unit processing 11,000 barrels of naphtha per day.

Table VIII Charge rate11,00tl b./s.d. Catalyst cost-$562 per cubic foot(c.l.)

a pressure of about 15 150 p.s.i.g. and an average reactor temperaturewithin the range about 810 to about 980 F. to provide a maximumon-stream period between regenerations preferably of at least 3 dayswhen producing products having an octane rating of about 106, andgreater than 3 days when producing products having octane ratings ofless than 106, dependent upon the space velocity, said reactortemperature being dependent upon the octane rating of said product andsaid gasoline boiling range constituents of said high pressure efiiuent.

Furthermore, the present invention provides for reforming naphtha in alow pressure reforming unit at low pressure, i.e., within the range ofabout 15 to about 450 p.s.i. g in the presence of hydrogen andparticleform noble metal type reforming catalyst and correlating theoctane rating of the gasoline hydrocarbons of the charge to said lowpressure reforming unit with the required octane of the 10 RVP gasoline(containing process butanes) produced in said low pressure reformingunit and the reaction temperature in said low pressure unit, saidgasoline hydrocarbons in said charge to said low pressure unit having anoctane rating of at least about 81 and not greater than about 98 for loWpressure unit 10 RVP gasoline having octane ratings of about 100 toabout 110.

On the other hand, the present invention provides for reforming naphthain a low pressure reforming unit at low pressure, i.e., within the rangeof about 15 to about 450 psig in the presence of hydrogen employing alligh Pressure Unit Combination Unit Low Pressure Unit Space CosttlifTcr- C1. of (1.1. of Velocity 5 C1. 01' Ci. of 0.1. 01 (lost ential,51M 1 Catalyst 1 Catalyst 7 Catalyst Catalyst Catalyst 2 Dlll at 0.75 at0.6 antral S.V. 111 L1 S.V. .BM 1

1, 280 3, 430 3 3 2. 150 4, 290 2. 140 1, 200 1, 500 3, 430 4 3 1, 9304, 200 2, 300 1, 325 l, 625 d, 430 5 3 1, 805 4, 290 2, 485 l, 400 1,010 3. 430 3 4 1, 820 4, 200 2, 470 1, 390 l, 820 3. 430 4 4 1, 610 4.200 2, 080 l. 505 l, 950 3, 430 5 4 1, 480 4. 200 2, 810 1, 580

$M=in thousands of dollars. I Additional catalyst. 3 1lP=high pressure;LP=low pressure.

The foregoing description of the present invention will be recognized bythose skilled in the art as a description of an improvement in lowpressure reforming in the presence of particle-form platinum-typereforming catalyst to produce gasoline containing process-butanes havingoctane ratings of at least 100 which comprises introducing into areforming reactor under a pressure less than 500 p.s.i.g., for example,100-300 p.s.i.g. containing particle-form platinum-type reformingcatalyst, a charge stock having an octane rating of at least about 81and not greater than about 98 and hydrogen and correlating the octanerating of said charge stock with the required octane rating of theproduct and the reaction temperature to provide a maximum on-streamperiod between regenerations preferably of at least about 3 days whenproducing products having an octane rating of about 106, and greaterthan 3 days when producing products having octane ratings of less than106 depending upon the space velocity employed. The present inventionalso provides for reforming a charge stock having an octane rating lessthan 81 at pressure of at least 500 psig in the presence ofparticle-form reforming catalyst and hydrogen to produce a high pressureeflluent the gasoline hydrocarbons of which have an octane rating withinthe range of about 81 to about 98, reducing the pressure of said highpressure eflluent, reforming said high pressure ellluent in the presenceOf pafliclerfwm Platinum-type reforming catalyst at particle-form solidnoble metal reforming catalyst, relatively high reaction temperatures,and relatively short onstream periods, and correlating the octane ratingof the gasoline hydrocarbons of the charge to said low pressurereforming unit with the required octane rating of the 10 RVP gasoline(containing process butanes) and the reaction temperature in said lowpressure unit to employ less catalyst per unit throughput to producesaid 10 RVP gasoline having said required octane rating than whennaphtha is reformed to said 10 RVP gasoline having said required octanerating without correlating the aforesaid octane rating of the gasolinehydrocarbons of the charge to said low pressure unit with the octanerating of at least of the 10 RVP gasoline (containing process butanes)produced in said low pressure unit, said gasoline hydrocarbons in saidcharge to said low pressure unit having an octane rating of at leastabout 81 and not greater than about 98 for low pressure unit 10 RVPgasoline having octane ratings of about 100 to about 110. In addition,the present invention provides for reforming naphtha in a high pressurereforming unit in the presence of hydrogen and particle-form reformingcatalyst and regulating the catalyst-to-oil ratio and reactiontemperature to produce a EAT equal to at least 2N F. (as definedhereinbefore) across the reactor or reactors of the high pressurereforming unit to produce a high pressure unit elllucnt, reducing thepressure of said high pressure effluent to that of a low pressurereforming unit, reforming said high pressure effluent in said lowpressure reforming unit at pressures less than 500 psig. in the presenceof particle-form solid reforming catalyst and regulating thecatalyst-to-oil ratio and the reaction temperature in said low pressurereforming unit to produce a EAT not greater than about N F. (as definedhereinbefore) across the reactor or reactors of said low pressurereforming unit, and recovering gasoline having an octane rating of atleast 100. The present invention also provides for reforming naphthacomprising naphthenes and parafiins in a high pressure reforming unit atpressures of at least 500 p-.s.i.g. in the presence of hydrogen andparticle form solid reforming catalyst at reforming temperature andspace velocity to convert a preponderant portion of said naphthenes toaromatic hydrocarbons and to produce a high pressure effluent, reducingthe pressure of said high pressure effluent to that of a low pressure rcforming unit, contacting said high pressure effluent under pressure lessthan about 509 p.s.i.g. with particle-form solid reforming catalystunder reforming conditions of temperature and space velocity to produceRVP gasoline (containing process butanes) having an octane rating of atleast 100, and correlating the octane rating within the range of about81 to about 98 of the gasoline hydrocarbons in said high pressureeffluent with the volume of catalyst in said low pressure reforming unitto produce said 10 RVP gasoline having the required octane rating.

We claim:

1. The method of producing gasoline having an octane rating of 100 toabout 110 which comprises establishing a plurality of high pressurereforming zones each containing particle-form solid reforming catalystand piped for series flow of fluid reactant from the first high pressurereforming Zone to the last high pressure reforming zone of the aforesaidplurality of high pressure refonming zones, establishing a plurality oflow pressure reforming zones each containing particle-form solidreforming catalyst and piped for series flow of fluid reactant from thefirst low pressure reforming zone to the last low pressure reformingzone of the aforesaid plurality of low pressure reforming zones,introducing charge naphtha into the aforesaid first high pressurereforming zone, contacting said charge naphtha in each of the aforesaidplurality of high pressure reforming zones with the aforesaidparticleform solid reforming catalyst in the presence of hydrogen underreforming conditions of temperature, space velocity and pressure of atleast 500 p.s.i.g., regulating the catalystto-naphtha ratio in each ofthe aforesaid high pressure reforming zones to obtain a difference intemperature between the temperature of the vapors entering each highpressure reforming zone and the temperature of the vapors leaving thesame high pressure reforming zone and to obtain a sum in degreesFahrenheit of the aforesaid differences in temperature for all of theaforesaid high pressure reforming zones equal to at least twice thenumerical value of the concentration of naphthenes in the aforesaidcharge naphtha, withdrawing the aforesaid last high pressure reformingzone a high pressure effluent comprising hydrogen and C and heavierhydrocarbons boiling in the gasoline boiling range, introducing at leastthat portion of the aforesaid high pressure comprising hydrocarbonsboiling in the gasoline boiling range at a pressure less than 500p.s.i.g. into the aforesaid first low pressure reforming zone,contacting the aforesaid portion of the aforesaid high pressure effluentin each of the low pressure reforming zones of the aforesaid pluralityof low pressure reforming zones with partiole-fonm solidplatinum-containing reforming catalyst in the presence of hydrogen underreforming conditions of temperature, space velocity and pressure lessthan 500 p.s.i.g., regulating the catalyst-to-naphtha ratio in each ofthe aforesaid low pressure reforming zones to obtain a difference intempcrture between the temperature of the vapors entering each lowpressure reforming zone and the temperature of the vapors leaving thesame low pressure reforming zone and to obtain a sum in degreesFahrenheit of the aforesaid dilferences in temperature for all of theaforesaid low pressure reforming zones not greater than the numericalvalue of the concentration of naphthenes in the aforesaid chargenaphtha, withdrawing from the aforesaid last low pressure reforming zoneof the aforesaid plurality of low pressure reforming zones a finaleffluent comprising hydrogen, and C and heavier hydrocarbons boiling inthe gasoline boiling range and recovering from said final efiluent l0RVP gasoline having an octane rating of with a yield of about 96 percentto about with a yield of about 76 percent.

2. A method of producing 10 RVP leaded gasoline having an octane ratingof a least 100 which comprises contacting in a first reforming stagecomprising a plurality of reforming zones piped for series flow of fluidreactant from a lead reforming zone to a tail reforming zone chargenaphtha and particle-form solid noble metal reforming catalyst in thepresence of hydrogen at reforming temperature, reforming pressure of atleast 500 p.s.i.g. and a reforming space velocity of at least 3,withdrawing from the aforesaid tail reforming zone in said firstreforming stage a high pressure effluent comprising hydrogen andhydrocarbons boiling in the gasoline boiling range having an octanerating within the range of about 86 to 98, contacting in the presence ofhydrogen in a second reforming stage comprising a plurality of reformingzones piped for series flow of fluid reactant from a lead reforming zoneto a tail reforming zone a second stage charge mixture comprising atleast the hydrocarbons boiling in the gasoline boiling range of theaforesaid high pressure effluent with particle-form solid noble metalreforming catalyst at reforming temperature, reforming pressure lessthan 500 p.s.i.g., and reforming space velocity of at least 3,withdrawing from the aforesaid tail reforming zone in the aforesaidsecond stage a final effluent comprising hydrogen, and C and heavierhydrocarbons boiling in the gasoline boiling range, and recovering fromsaid final efiluent 10 RV? leaded gasoline having an octane rating of100 with a yield of about 96 percent to about 110 with a yield of about76 percent.

3. The method set forth and described in claim '2 wherein the noblemetal reforming catalyst is a platinum reforming catalyst.

4. The method set forth and described in claim 2 wherein the noble metalreforming catalyst is a platinum reforming catalyst, and wherein thesecond stage charge mixture comprises extraneous unreformed mixture ofhydrocarbons boiling in the gasoline boiling range and at least thehydrocarbons boiling in the gasoline boiling range from the aforesaidhigh pressure effluent, the hydrocarbons boiling in the gasoline boilingrange of thc aforesaid second stage charge mixture having an octanerating of 81 to 98.

5. A method of producing 10 RVP gasoline having an octane rating(research-k3 cc. TEL), hereinafter desig nated leaded gasoline, withinthe range of about 100 to about H0 in two stages to provide maximumon-stream time in the second of the aforesaid two stages when producingleaded gasoline having an octane rating within the aforesaid range whichcomprises contacting naphtha in a first, high pressure, stage withstatic particle-form solid reforming catalyst in the presence ofhydrogen under reforming pressure of at least 509 p.s.i.g., at reformingtemperature, and liquid hourly space velocity to produce a first, highpressure, stage eflluent, regulating the aforesaid temperature and spacevelocity to obtain hydrocarbons boiling in the gasoline boiling range,hereinafter designated gasoline hydrocarbons, having an octane ratingwithin the range of about 90 to 98, contacting in the presence ofhydrogen at least the gasoline hydrocarbons having an octane ratingwithin the range of about 90 to 98 of the aforesaid first, highpressure, stage cfiluent in a second, low pressure stage with staticparticle-form solid reforming catalyst comprising 0.35 to 2.0 percent byweight of platinum on alumina support under reforming pressure less than500 p.s.i.g., at reforming temperature and at reforming liquid hourlyspace velocity to obtain a second, low pressure, stage eflluent, andrecovering from said second, low pressure, stage eflluent a gasolinecomprising C and heavier hydrocarbons boiling in the gasoline boilingrange having a Reid vapor pressure of ten pounds and having an octanerating (research-i-3 cc. TEL) within the range of 100 with a yield ofabout 96 percent to about 110 with a yield of about 76 percent.

6. The method of producing 10 RVP gasoline having an octane rating(research+3 cc. TEL) within the range of about 100 to about 110 as setforth and described in claim 5 wherein the reforming temperature andspace velocity in the first, high pressure, stage are regulated toobtain gasoline hydrocarbons having an octane rating within the range of94 to 95, wherein the RVP leaded gasoline has an octane rating of 101 to107, and wherein the on-stream time in the second, low, pressure stageis about ten days when producing 10 RVP leaded gasoline having an octanerating of 107 to about 127 days when producing 10 RVP leaded gasolinehaving an octane rating of 101.

7. In the method of reforming naphtha at reactor pressures less than 500p.s.i.g. to obtain 10 RVP leaded .gasoline having an octane rating of atleast 100 which comprises contacting charge naphtha comprisingnaphthenes and paraflins with particle-form solid platinum-group metalreforming catalyst in the presence of hydrogen at reforming conditionsof temperature and space velocity to produce 10 RVP leaded gasolinehaving an octane rating of 100 to 110, the improvement which comprisesregulating the octane rating of the aforesaid charge naphtha Within therange of 85 to 98 dependent upon the required octane rating of at least100 of the 10 RVP leaded gasoline product, and contacting the aforesaidcharge naphtha having the aforesaid regulated octane rating with theaforesaid platinum-group metal reforming catalyst at the lowestreforming temperature, dependent upon the aforesaid regulated octanerating of the aforesaid charge naphtha and the octane rating of theaforesaid l0 RVP leaded gasoline product to produce the aforesaid 10 RVPleaded gasoline product in a yield greater than that obtained whenreforming the aforesaid charge naphtha in the presence I of hydrogen andthe aforesaid platinum-group metal reforming catalyst at 500 p.s.i.g.and for longer on-stream time between regenerations of the aforesaidplatinumgroup metal reforming catalyst than is obtained when reformingthe aforesaid charge naphtha without regulating the octane ratingthereof within the range 85 to 98 dependent upon the octane rating ofthe 10 RVP leaded gasoline product in the presence of the aforesaidplatinumgroup metal reforming catalyst at the same reforming pressureless than 500 p.s.i.g. to produce 10 RVP leaded gasoline having the sameoctane rating as the aforesaid 10 RVP leaded gasoline product.

8. The improvement in the method of reforming naphtha at reactorpressures less than 500 p.s.i.g. as set forth in claim 7 wherein thecharge naphtha having the regulated octane rating within the range of 85to 98 contains less than 20 parts per million of sulfur, less than 1part per million of nitrogen, and less than 0.5 part per billion ofarsenic.

9. The method of producing 10 RVP leaded gasoline product containingprocess produced butanes and having an octane rating of 100 to 110 fromthe product of the low pressure stage of a two-stage reforming processin which the pressure in the first high pressure stage is a reformingpressure of at least 500 p.s.i.g. and the pressure in the second lowpressure stage is a reforming pressure less than 500 p.s.i.g. whichcomprises contacting naphtha containing naphthenes, less than 20 partsper million of sulfur, not more than 1 part per million of nitrogen, andless than 0.5 part per billion of arsenic in a first stage high pressurereforming zone in the presence of hydrogen with particle-form solidreforming catalyst at a reforming pressure of at least 500 p.s.i.g. atreforming conditions of temperature and space velocity dependent uponthe activity of the aforesaid reforming catalyst to obtain a highpressure effluent the gasoline hydrocarbons of which have an octanerating dependent upon the octane rating of the product of the lowpres-sure stage within the range of to 98, reducing the pressure of theaforesaid high pressure eflluent, contacting at least the gasolinehydrocarbons of the aforesaid high pressure effluent in a second stagelow pressure reforming zone at a low pressure reforming zone pressurenot greater than about 350 p.s.i.g. with particle-form noble metalreforming catalyst at reforming space velocity and minimum reformingtemperature de pendent upon the octane rating of the gasoline hydrocarbons of the aforesaid high pressure efiluent, the octane rating ofthe 10 RVP leaded gasoline product, and the aforesaid space velocity toproduce 10 RVP leaded gasoline product having an octane rating of to110, and recovering l0 RVP leaded gasoline, containing process producedbutanes, having an octane rating of 100 to in a yield greater than theyield when the aforesaid charge naphtha is reformed at reformingpressure of at least 500 p.s.i.g. to 10 RVP leaded gasoline product inthe presence of the aforesaid noble metal reforming catalyst and with anon-strearn time between regenerations of catalyst in the second lowpressure stage reforming zone greater than the on-stream time betweenregenerations of the aforesaid noble metal reforming catalyst whenreforming the aforesaid charge naphtha without regulating the octanerating thereof within the range 85 to 98 dependent upon the octanerating of the 10 RVP leaded gasoline in the presence of the aforesaidreforming catalyst at the same reforming pressure not greater than about350 p.sig. to 10 RVP leaded gasoline having the same octane rating.

10. The method of producing 10 RVP leaded gasoline product containingprocess produced butanes and having an octane rating of 100 to 110 fromthe product of the low pressure stage of a two-stage reforming processas set forth and described in claim 9 wherein the particle'- form solidreforming catalyst in the first high pressure stage and theparticle-form solid reforming catalyst in the second low pressure stageare platinum metal reforming catalysts comprising about 0.35 to about1.0 percent by weight of platinum, about 0.35 to about 1.0 percent byweight of chlorine, on an alumina support.

11. The method of producing leaded gasoline having an octane rating ofabout 100 to 110 and containing process-produced butanes which comprisescontacting gasoline hydrocarbons having an octane rating Within therange of 86 to 98 dependent upon the octane rating of the leadedgasoline product with particle form solid plattinum-group metalreforming catalyst in the presence of hydrogen at reaction pressures of15 to 450 p.s.i.g., at space velocities of about 0.5 to 5.0, and at areforming temperature dependent upon the octane rating of the aforesaidgasoline hydrocarbons and the octane rating of the aforesaid 10 RVPleaded gasoline product to obtain 10 RVP leaded gasoline product havingan octane rating of 100 to 110 with longer on-stream periods betweenregenenations than when reforming at a pressure within the range of 15to 450 p.s.i.g. gasoline hydrocarbons having an octane rating notdependent upon the octane rating of the 10 RVP leaded gasoline product.

12. The method set forth and described in claim 11 wherein theparticle-form solid platinum-group metal reforming catalyst comprises0.35 to 2 percent by weight of platinum on alumina support and thereforming temperature is within the range of 824 F. and 948 F. whenusing virgin or freshly regenerated catalyst.

13. The method set forth and described in claim 1 wherein the reformingcatalyst in both the high pressure 21 22 reforming zones and the lowpressure reforming zones 2,710,827 Gornowski June 14, 1955 comprisesabout 0.35 to about 2.0 percent by Weight of 2,758,062 Arundale et Allg-1956 platinum on alumina support, 2,758,063 MacLaren et a1. Aug. 7, 19562,862,872 Beekberger Dec. 2, 1958 References Cited in the file of thispatent 5 2,865,837 Holcomb et a1 Dec. 23, 1958 UNITED STATES PATENTSFOREIGN PATENTS 2,642,381 Dickinson June 16, 1953 714,061 Great BritainAug. 25, 1954 2,642,384 Cox June 16, 1953 745,520 Great Britain Feb. 29,1956 2,654,694 Berger et a1. Oct. 6, 1953 10 538,992 Canada Apr. 2, 1957

1. THE METHOD OF PRODUCING GASOLINE HAVING AN OCTANE RATING OF 100 TOABOUT 110 WHICH COMPRISES ESTABLISHING A PLURALTIY OF HIGH PRESSUREREFORMING ZONES EACH CONTAINING PARTRICLE-FORM SOLID REFORMING CATALYSTAND PIPED FOR SERIES FLOW OF FLUID REACTANT FROM THE FIRST HIGH PRESSUREREFORMING ZONE TO THE LAST HIGH PRESSURE REFORMING ZONE OF THE AFORESAIDPLURALITY OF HIGH PRESSURE REFORMING ZONES, ESTABLISHING A PLURALITY OFLOW PRESSURE REFORMING ZONES EACH CONTAINING PARTICLE-FORM SOLIDREFORMING CATALYST AND PIPED FOR SERIES FLOW OF FLUID REACTANT FROM THEFIRST LOW PRESSURE REFOMING ZONE TO THE LAST LOW PRESSURE REFORMING ZONEOF THE AFORESAID PLURALITY OF LOW PRESSURE REFORMING ZONES, INTRODUCINGCHARGE NAPHTHA INTO THE AFORESAID FIRST HIGH PRESSURE REFORMING ZONE,CONTACTING SAID CHARGE NAPHTHA IN EACH OF THE AFORESAID PLURALITY OFHIGH PRESSURE REFORMING ZONES WITH THE AFORESAID PARTICLEFORM SOLIDREFORMING CATALYST IN THE PRESENCE OF HYDROGEN UNDER REFORMINGCONDITIONS OF TEMPERATURE, SPACE VELOCITY AND PRESSURE OF AT LEAST 500P.S.I.G., REGULATING THE CATALYSTTO-NAPHTHA RATIO IN EACH OF THEAFORESAID HIGH PRESSURE REFORMING ZONES TO OBTAIN A DIFFERENCE INTEMPERATURE BETWEEN THE TEMPERATURE OF THE VAPORS ENTERING EACH HIGHPRESSURE REFORMING ZONE AND THE TEMPERATURE OF THE VAPORS LEAVING THESAME HIGH PRESSURE REFORMING ZONE AND TO OBTAIN A SUM IN DEGREESFAHRENHEIT OF THE AFORESAID DIFFERENCES IN TEMPERATURE FOR ALL OF THEAFORESAID HIGH PRESSURE REFORMING ZONES EQUAL TO AT LEAST TWICE THENUMERICAL VALUE OF THE CONCENTRATION OF NAPHTHENES IN THE AFORESAIDCHARGE NAPHTHA, WITHDRAWIGN THE AFORESAID LAST HIGH PRESSURE REFORMINGZONE A HIGH PRESSURE EFFLUENT COMPRISING HYDROGEN AND C1 ANDHEAVIERHYDROCARBONS BOILING IN THE GASOLINE BOILING RANGE, INTRODUCING AT LEASTTHAT PORTION OF THE AFORESAID HIGH PRESSURE COMPRISING HYDROCARBONSBOILING IN THE GASOLINE BOILING RANGE AT A PRESSURE LESS THAN 500P.S.I.G. INTO THE AFORESAID FIRST LOW PRESSURE REFORMIGN ZONE,CONTACTING THE AFORESAID PORTION OF THE AFORESAID HIGH PRESSURE EFFLUENTIN EACH OF THE LOW PRESSURE REFORMING ZONES OF THE AFOESAID PLURALITY OFLOW PRESSURE REFORMING ZONES WITH PARTICLE-FORM SOLIDPLATINUM-CONTAINING REFORMING CATALYST IN THE PRESENCE OF HYDROGEN UNDERREFORMING CONDITIONS OF TEMPERATURE, SPACE VELOCITY AND PRESSURE LESSTHAN 500 P.S.I.G., REGULATING THE CATALYST-TO-NAPHTHA RATIO IN EACH OFTHE AFORESAID LOW PRESSURE REFORMING ZONES TO OBTAIN A DIFFERENCE INTEMPERTURE BVETWEEN THE TEMPERATURE OF THE VAPORS ENTERING EACH LOWPRESSURE REFORMING ZONE AND THE TEMPERATURE OF THE VAPORS LEAVING THESAME LOW PRESSURE REFORMING ZONE AND TO OBTAIN A SUM IN DEGREESFAHRENHEIT OF THE AFORESAID DIFFERENCES IN TEMPERATURE FOR ALL OF THEAFORESAID LOW PRESSURE REFORMING ZONES NOT GREATER THAN THE NUMERICALVALUE OF THE CONCENTRATION OF NAPHTHENES IN THE AFOESAID CHARGE NAPHTHA,WITHDRAWING FROM THE AFORESAID LAST LOW PRESSURE REFORMING ZONES A FINALEFFLUENT COMPRISING HYDROGEN, AND C4 AND HEAVIER HYDROCARBONS BOILING INTHE GASOLINE BOILING RANGE AND RECOVERING FROM SAID FINAL EFFLUENT 10RVPGASOLINE HAVING ANOCTANE RATING OF 100 WITH A YIELD OF ABOUT 96 PERCENTTO ABOUT 110 WITH A YIELD OF ABOUT 76 PERCENT.